Prediction And Analysis For The Intake And Exhaust Noise Characteristics Of Turbocharged Diesel Engine

Turbo-charged diesel engine is widely used in automobile,power generation,ship,and other industries.The intake and exhaust noise control is concerned by scholars all over the word.The main method of reducing the intake and exhaust noise of turbo-charged diesel engine is to install the silencing system.But the installation of the intake and exhaust silencing system will affect the dynamic and economy performance of the diesel engine.In this thesis,a turbo-charged diesel engine is simulated by GT-Power software on the basis of experimental data.The basic process of model establishment is introduced in detail,the model is checked,and the performance parameters of diesel engine are extracted.The influence of the revolution and load on the intake and exhaust noise is studied on the simulation and calculations.It is found that when the load remains unchanged and the number of revolutions increases,the sound pressure levels of the intake and exhaust noise increase,the central frequency of the peak noise moves backwards,and the amplitude of the noise increases slightly.In the opposite case,the frequency of the intake and exhaust noise peak is the same,and the noise peak and total sound pressure increase as the load increases.In the process of research of silencing system,the transmission loss of typical resistant and resistive silencing system models is calculated.The one-dimensional time domain method is compared with the three-dimensional finite element method.The result proves that the one-dimensional time domain method has high reliability in the low frequency domain,on the basis of which,a resistant exhaust silencing system is designed according to the spectrum characteristics of exhaust noise.The design process of the resistant expansion chamber silencing system is introduced in detail,which makes the exhaust noise well controlled.In order to explore the influence of intake and exhaust silencing system on the performance of diesel engine,the intake air filter and the intake muffler model are established respectively.At the same time,the model of the exhaust noise reduction system,including the catalytic converter and the exhaust silencing system,is established.It is found that when intake silencing system is added,intake pressure decreases slightly,which resulted in a slight decrease in the power.The exhaust silencing system has a large impact on the engine performance,it will increase the exhaust backpressure,which will resulted in the decreasing of the power and torque.Therefore,when the exhaust silencing system is designed,theperformance of the noise reduction and the engine's dynamic performance should be taken into comprehensive consideration.Insertion loss is an important index to evaluate silencing system's acoustic attenuation performance,and the source impedance should be obtained when calculating the insertion loss.In this paper,the intake and exhaust sound source impedance of turbocharged diesel engine is extracted by using two load method in GT-Power.The method of calculating the sound source impedance is optimized by using the method of data statistics.The influence of the revolutions,load and turbo-charged system on the intake and exhaust sound source impedance is studied.